<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body, html {
            margin: 0;
            padding: 0;
            height: 100%;
        }

        .header, .footer {
            height: 40px;
            width: 100%;
            background: red;
        }

        .container {
            display: flex;
            height: calc(100% - 80px);
        }

        .middle {
            flex: 1;
            background: yellow;
        }

        .left {
            width: 200px;
            background: pink;
        }

        .right {
            background: aqua;
            width: 300px;
        }

    </style>
</head>
<body>
<div class="header">这里是头部</div>
<div class="container">
    <div class="left">左边</div>
    <div class="middle">中间部分</div>
    <div class="right">右边</div>
</div>
<div class="footer">这里是底部</div>
</body>
</html>
